Cardiovascular responses to heat acclimatisation in athletes with spinal cord injury

To determine the effect of heat acclimatisation (HA) training on blood profile and resting cardiac function in elite athletes with spinal cord injury (SCI). Quasi-experimental. Eleven athletes (10m, 1f) with SCI (C5-T3) completed a five-day isothermic HA protocol whereby gastrointestinal temperature (Tc) was elevated to and maintained at ∼38.5 degrees Celsius (°C) via intermittent exercise for sixty minutes each day. Blood samples were collected pre- and post-HA to determine changes in plasma volume (PV). Doppler ultrasound of the left-ventricular outflow tract and 2-d speckle tracking echocardiography were performed in a subset of athletes (n=5) to determine changes in indices of resting left-ventricular function and mechanics, respectively. Ten athletes were successfully able to raise and maintain Tc to 38.5°C. There was a non-significant increase in PV with HA training (ΔPV%: 3.0±5.4%, p=0.086). Following HA, resting HR decreased (63±4 pre-HA vs. 58±5 bpm post-HA, p=0.020), velocity time integral (21.4±2.7 vs. 23.7±3.0cm, p=0.045) and stroke volume increased (64.8±7.6 vs. 70.2±10.5mL, p=0.055). Our findings suggest a short-term HA protocol in athletes with SCI is safe and may induce beneficial changes in indices of resting left-ventricular function — however results are highly individualized. Future studies on HA in athletes with SCI should focus on determining mechanisms of adaptation and performance outcomes.